This invention relates to wheeled vehicles for conveying loads and, more particularly, to manually propelled wheeled carts for transporting loads, commonly referred to as hand trucks. Specifically, the invention is directed to a hand truck apparatus which can not only be used for transporting a load, but also can be used for lifting the load to a raised position, and which is configured such that the hand truck apparatus is self-stabilizing even if the load is in the raised position on the hand truck apparatus. The hand truck apparatus in accordance with the invention is especially advantageous during the transporting and installation of solid core doors, for example.
Various equipment is known for conveying loads. Hand trucks are one known type of equipment for transporting loads.
Typically, known hand trucks comprise an upright frame or chassis having a horizontal plate connected to the lower end of the chassis configured to be slid under a load. At least one, and typically two, wheels are connected to an axle mounted to the chassis rearwardly of the load supporting plate. The underside of the load supporting plate and the lower periphery of the wheels form a base for the hand truck such that the hand truck is self-stabilizing in the upright position whether or not a load is placed on the load supporting plate. The hand truck further includes a handle connected to the chassis.
In operation, a user places a load on the load supporting plate, stands on the side of the hand truck opposite the load supporting plate, grips the handle, and pulls the handle in order to lift the load suppporting plate from the ground such that the weight of the load is borne over the wheels. The wheels serve as a fulcrum for permitting the load to be leveraged from the ground. The hand truck can then be rolled on the wheels for transporting the load.
Some hand trucks further include runners connected to the chassis which extend away from the chassis beyond the outer periphery of the wheels. The runners allow the hand truck to be pulled by the user up an incline as a sled.
Unfortunately, the runners give the user no mechanical advantage in lifting the load. Furthermore, the hand truck is not in a self-stabilized condition while the load is being lifted.
Other equipment is known for lifting and transporting loads. Montour, U.S. Pat. No. 2,548,806, for example, discloses the use of two dollies each including load engaging elements configured to be slid under a load in a lowered position. The load engaging elements are vertically movable with respect to an upright frame. The dollies each include caster wheels mounted to the upright frame rearwardly of the load engaging elements. The dollies further each include a jack for raising the load engaging elements after the elements are inserted under a load for lifting the load. The load can then be transported.
Unfortunately, although the dollies disclosed in Montour, U.S. Pat. No. 2,548,806, are self-stabilized while the load engaging elements are in the lowered position, the dollies must be used in tandem in order to support a load in a stable condition when the load engaging elements are in a raised position. Since the dollies can only be used in pairs, the use of the dollies disclosed in Montour, U.S. Pat. No. 2,548,806, is limited; for example, the dollies cannot be used for transporting and installing solid core doors.
Solid core doors have heretofore been manually carried or else transported by known hand truck equipment in connection with the installation of the door. After the door is transported to the location of installation, at least two workers are needed for installing the door. Installation requires that hinge plates be attached to the edge of the door and that the door be manually lifted into position for also securing the hinge plates to the door frame. Precise positioning of the door with respect to the door frame is very difficult, especially in the case of two workers where one worker must secure the hinge plates to the door frame, as well as aid in lifting the door. Furthermore, the use of several workers to accomplish the task of door installation is costly.